Merge pull request zendframework/zendframework#2218 from marc-mabe/ca…

…che_optimisations

Cache: Minimized comparisons on getting serializer of serializer plugin

src/Storage/Plugin/PluginOptions.php

@@ -213,13 +213,16 @@ public function setSerializer($serializer)
      */
     public function getSerializer()
     {
-        if (is_string($this->serializer)) {
-            $options = $this->getSerializerOptions();
-            $this->setSerializer(SerializerFactory::factory($this->serializer, $options));
-        } elseif (null === $this->serializer) {
-            $this->setSerializer(SerializerFactory::getDefaultAdapter());
+        if (!$this->serializer instanceof SerializerAdapter) {
+            // use default serializer
+            if (!$this->serializer) {
+                $this->setSerializer(SerializerFactory::getDefaultAdapter());
+            // instantiate by class name + serializer_options
+            } else {
+                $options = $this->getSerializerOptions();
+                $this->setSerializer(SerializerFactory::factory($this->serializer, $options));
+            }
         }
-
         return $this->serializer;
     }